Fix `iter_on_single_items` FP on function pointers and let stmts (#15013)

Closes rust-lang/rust-clippy#14981

changelog: [`iter_on_single_items`] fix FP on function pointers and let
stmts

2 files changed, 48 insertions, 0 deletions

diff --git a/tests/ui/iter_on_single_items.fixed b/tests/ui/iter_on_single_items.fixed
index b43fad6449c..044037aac2e 100644
--- a/tests/ui/iter_on_single_items.fixed
+++ b/tests/ui/iter_on_single_items.fixed
@@ -66,3 +66,27 @@ fn main() {
     custom_option::custom_option();
     in_macros!();
 }
+
+mod issue14981 {
+    use std::option::IntoIter;
+    fn takes_into_iter(_: impl IntoIterator<Item = i32>) {}
+
+    fn let_stmt() {
+        macro_rules! x {
+            ($e:expr) => {
+                let _: IntoIter<i32> = $e;
+            };
+        }
+        x!(Some(5).into_iter());
+    }
+
+    fn fn_ptr() {
+        fn some_func(_: IntoIter<i32>) -> IntoIter<i32> {
+            todo!()
+        }
+        some_func(Some(5).into_iter());
+
+        const C: fn(IntoIter<i32>) -> IntoIter<i32> = <IntoIter<i32> as IntoIterator>::into_iter;
+        C(Some(5).into_iter());
+    }
+}
diff --git a/tests/ui/iter_on_single_items.rs b/tests/ui/iter_on_single_items.rs
index 625c96d3ef1..c925d0e480f 100644
--- a/tests/ui/iter_on_single_items.rs
+++ b/tests/ui/iter_on_single_items.rs
@@ -66,3 +66,27 @@ fn main() {
     custom_option::custom_option();
     in_macros!();
 }
+
+mod issue14981 {
+    use std::option::IntoIter;
+    fn takes_into_iter(_: impl IntoIterator<Item = i32>) {}
+
+    fn let_stmt() {
+        macro_rules! x {
+            ($e:expr) => {
+                let _: IntoIter<i32> = $e;
+            };
+        }
+        x!(Some(5).into_iter());
+    }
+
+    fn fn_ptr() {
+        fn some_func(_: IntoIter<i32>) -> IntoIter<i32> {
+            todo!()
+        }
+        some_func(Some(5).into_iter());
+
+        const C: fn(IntoIter<i32>) -> IntoIter<i32> = <IntoIter<i32> as IntoIterator>::into_iter;
+        C(Some(5).into_iter());
+    }
+}